1. Field of the Invention
The present invention relates to a rechargeable battery.
2. Description of the Related Art
A rechargeable battery can be repeatedly charged and discharged, unlike a primary battery that is not designed to be recharged. A rechargeable battery having a small capacity is used for a small portable electronic device like a mobile phone or a laptop computer and a camcorder, and a rechargeable battery having a large capacity is widely used as a power source for driving a motor of a hybrid vehicle.
A nickel-cadmium (Ni—Cd) battery, a nickel-metal hydride (Ni-MH) battery, a lithium (Li) battery, and a lithium ion (Li-ion) rechargeable battery are each available rechargeable batteries. Particularly, the Li-ion rechargeable battery has an operation voltage that is about 3 times greater than the operation voltage of a Ni—Cd battery and of a Ni-MH battery, which are all widely used as a portable electronic equipment power source. Further, due to a high energy density per unit weight, the Li-ion rechargeable battery is widely used.
The rechargeable battery generally uses a lithium-based oxide as a positive electrode active material and a carbon material as a negative electrode active material. In general, the rechargeable battery is classified into a liquid electrolyte battery and a polymer electrolyte battery according to a type of electrolyte used. A battery using a liquid electrolyte is referred to as a Li-ion battery, and a battery using a polymer electrolyte is referred to as a lithium polymer battery.
For instances when an internal pressure exceeds a predetermined pressure, a rechargeable battery includes a vent hole that discharges the internal pressure and a vent plate that closes and seals the vent hole. When an internal pressure of the rechargeable battery exceeds a predetermined pressure, the vent plate is cut out to open the vent hole.
However, when an impact is applied from the outside of the rechargeable battery, the vent plate may be abnormally fractured regardless of an internal pressure of the rechargeable battery.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form prior art.